


The Side Effects of Dimensional Travel: A One-Man Case Study

by VoidfishDuet



Category: Yu-Gi-Oh! Duel Monsters (Anime & Manga)
Genre: DSOD is about grieving and Kaiba's afterlife trip was basically a suicide attempt and here's why, Gen, Hospitals, M/M, Past Character Death, Past One-Sided Prideshipping (if you squint), Pre-Relationship, Self Harm, Suicidal Ideation, post-dsod, rivalshipping - Freeform
Language: English
Status: Completed
Published: 2021-03-14
Updated: 2021-03-14
Packaged: 2021-03-22 13:01:04
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,043
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/30039087
Author URL: https://archiveofourown.org/users/VoidfishDuet/pseuds/VoidfishDuet
Summary: In which Seto returns from the afterlife, Yugi reminds him that his actions have consequences, and the two of them realize his cross-dimensional journey is startlingly similar to a different type of journey.
Relationships: Kaiba Seto/Mutou Yuugi
Comments: 2
Kudos: 17





	The Side Effects of Dimensional Travel: A One-Man Case Study

**Author's Note:**

> Based on [this](https://0atk.tumblr.com/post/631115823743893504/welcome-back-to-this-dimensionrel=) incredible piece of fanart. Thank you to Cassie for your beta services! Sorry for making Seto so sad, but I just have to. Warning for suicidal ideation, self harm, and general sadness.

Everything hurt. In the days since he had returned to Earth, this was the one constant Seto could find; from his neck down to his feet, he ached. This was a valuable piece of data, for even if it was for personal gain, his journey across dimensions was still an experiment, at its core. And the soreness of his body was certainly a dramatic side effect. He had noted it down in a word document on his laptop: _full-body muscular pain, present_ ~~_two_ _three_~~ _four days after voyage._

The remark was the latest in a bulleted list he was compiling, which he was hoping to format and submit to any academic publication that would accept it. Not that he figured he would have much trouble getting it published; journals would be at one another’s throats for the chance to publish such bleeding edge research, especially when it was carried out by someone famous. He laughed aloud at the thought, wincing when it jostled his head a little too much. _Headache, made worse by sharp movements—possibly related to aforementioned muscular pain._

He shifted in his bed, wishing it were more adjustable so that he wasn’t hunched uncomfortably over his laptop. Despite his protests that the Kaiba Corp medical staff were more than competent enough to look over him upon his return from Aaru, Mokuba had insisted that he go to “a real hospital” instead. Seto would have put up more of a fight, but he was slightly delirious and totally fixated on how much it _hurt_. Before he knew it, he was in the backseat of a limo, being driven by Isono to Domino City Hospital. Of course, it didn’t offer nearly the same comfort that being treated at his own home would. Case in point—the godforsaken bed, and its lack of range of motion.

The rest of the room was similarly mediocre; he looked around, in the vain hope that anything had changed, but he was disappointed. Off-white walls; a desk under a large window, with two uncomfortable-looking chairs on either side; a small television set up in the intersection of two walls, currently showing financial news on mute; a closet where his coat and other clothes were hung, ready to be worn. _Wait for me_ , he told his coat in his head; it would be back on his person again just as soon as they let him out of this place.

The neck brace they had stuck him in was chafing, now; his movements must have caused it to fall into an uncomfortable position. _Minor fractures of cervical vertebrae 2 and 3—whiplash from re-entry?_ He reached up to re-adjust it with his right hand, but stopped short when he remembered the IV stuck into his vein— _dehydration, likely present prior to travel and exacerbated by it_ —and switched to his left, pulling the brace down with a soft grunt. Better, but still not comfortable.

He switched from his list to his email; he was still going through the backlog of information he had missed in the six months he had spent in Aaru. While he was with _Him_ , only an hour had passed. _Time dilation—further research necessary into this subject._ At any rate, despite Mokuba acting as President, he had continued to receive emails while he was gone. They were mostly newsletters he had subscribed to, or scam artists pretending that he had won a cruise or had a vast sum of money in a foreign country, but some were personal.

Mazaki, for instance, had left him a long note, essentially detailing their entire history together and saying she “wished she had gotten to talk to him more.” It sounded like something written in a yearbook, but Seto read it twice anyway.

More surprising was a message from Isis Ishtar, who had sent him an invitation to the opening of a new exhibit at the Egyptian Museum in Cairo based on the new information about the so-called Nameless Pharaoh. It was a standard invite, until the very last sentence: “Please attend if you are able; I believe _He_ would have wanted you to come.” Too bad, really—the email was dated for the third month of his absence. _Missing out on events (see “time dilation”)._

His voicemails had been…more difficult to go through. So far, he had only been able to listen to three, and even then, he had to take breaks. _Trouble with hearing familiar voices, causes diffuse ache in chest—more research needed._

“Listen Kaiba, I dunno how you got to where you are, but you better come the fuck back, or I swear, I’ll come to the afterlife and beat the shit out of you personally. Don’t test me, rich boy.”

“Hi Kaiba, it’s Yugi. Um, it’s been about—six weeks? Yeah, that sounds right—since you left. Um, I’m taking over as Acting VP, since Mokuba needed help with, you know, everything. Uh, I hope you aren’t gone for much longer, ‘cause things really aren’t going so well.”

“Seto—big brother—please, come home.”

A knock on the door startled Seto out of his thoughts; he cleared his throat, swallowing around the sudden lump that had formed there. Already, he was suspicious; the nurses and doctors usually announced themselves along with knocking, and Mokuba walked right in. No one else had come to visit him, but he supposed there was a first time for everything.

“Yes?” he said, wishing his voice didn’t sound so hoarse. Instead of a response, the door swung open, revealing the slight form of Yugi Mutou. Gently, he closed the door behind him, then made his way in until he stood at the foot of Seto’s hospital bed.

He wasn’t wearing his school uniform, which was a mild surprise. Instead, he wore a dark woolen coat over his leather pants, and a checkered scarf was wound around his neck. Seto was shocked at how bundled up Yugi was, until took a moment to remind himself that it was nearly winter now, instead of late spring, when he had left this dimension.

“Hi, Kaiba.” Yugi gave him a small wave and a smile, though it didn’t reach his eyes. He set the messenger bag that had been slung over his right shoulder on one of the chairs, then unwound his scarf, revealing that yes, he was still wearing that ridiculous collar. “It’s, uh, good to see you.”

A simple greeting; Seto knew how to respond to this. All he had to do was open his mouth and say, “Nice to see you too.”

“Took you long enough,” Seto scoffed. That was not what he wanted to say. _Inappropriate speech patterns, despite normal MRI scans. Ask for second MRI scan._ Okay, he could try again. “I mean, I figured you would have come sooner, I guess.” Better, but still not friendly.

“I wanted to come as soon as Mokuba called me,” Yugi said, his brow furrowing underneath his bangs, “but I got caught up with some things at Kaiba Corp. You have a nice office, by the way.” He laughed, though it wasn’t as light as Seto remembered it being, and his eyes were still untouched.

At the notification of a new email, Seto turned his gaze back to his laptop, though his brow furrowed at Yugi’s words. “Yes, I’m aware. Did Mokuba give you the grand tour while you were assisting him? I hope you didn’t break anything.”

He missed his office, but he wouldn’t say that to Yugi. It was too sentimental, and if there was one thing Seto Kaiba was known for, it was his lack of sentiment—for anything except Mokuba, of course. He would rather have one giant Achilles’ heel than hundreds of tiny vulnerabilities.

Yugi chuckled again, sounding closer to how he remembered, which made Seto look up to meet Yugi’s smirking face. “Actually, he’s letting me use it as my office. He figured the Acting VP should get some perks. I hope you don’t mind, but I took down all the Blue-Eyes decorations and replaced them with Kuriboh; it really brightens up the space.”

“I’m sorry, you did what?” Seto asked, louder than he meant to, which caused his vocal cords to twinge and trigger a momentary coughing fit. _Respiratory irritation, cause unclear. Could not possibly be the result of yelling at_ Him _during a duel in a desert climate._ Yugi kept smirking the whole time, even as he grabbed a plastic cup and filled it with tap water. When he finished coughing, Yugi offered him the cup, which he took reluctantly, sipping slowly so as to not accidentally choke.

“I’m kidding, Kaiba.” Yugi’s smile had transferred to his voice, audible even as Seto continued to clear his throat. “Well, about the Kuriboh stuff, anyway. I really am using your office.”

Seto’s hackles lowered, but only slightly. He drained the rest of the water, narrowing his eyes at Yugi over the rim of the cup, then set it down on the nightstand next to the hospital bed. He cleared his throat, hoping he sounded stronger when he next spoke.

“Why is Mokuba not using it?” he said, to prevent himself from demanding that Yugi get a new office immediately. That space had to be earned, and it had only been earned by him, to be passed down to Mokuba once he had earned it as well. Yugi Mutou was not in the line of succession. Then again, he did say Mokuba was in charge, so he could do whatever he pleased; yet, his stomach turned over at the thought of someone other than himself or his brother in the space he had worked so hard to maintain.

“He didn’t want it.” The sound of Yugi’s voice startled Seto; he didn’t realize he had gotten so deep in thought. _Decrease in attention span._

“What do you mean he didn’t want it? It’s the best office in the building.” Seto knew how he sounded; the constant questions, the increasingly petulant tone, he must have seemed to Yugi like the world’s most overgrown toddler.

Yugi’s smile fell with the grace of a Fabergé Egg knocked off a shelf by an earthquake. “He wouldn’t step foot in there, Kaiba,” he said, hands clenching by his sides. “Not once. He told me that it was still your office, that he couldn’t take it over, not when you would be back any day now. Eventually he let me use it, but only because I promised him that I was just watching it for you. Do you understand now?”

For a moment, they were both silent, Seto’s blank eyes staring into Yugi’s impassioned ones. Then, Seto looked back down at his computer, opening his document of side effects once more. _Breakdown in social relationships, related to—_

Suddenly, the lid of his laptop came crashing down, Seto only just managing to prevent his fingers from being crushed. The jolt took his hand far enough away that it tugged at his IV, a sharp pain adding itself to the ache he felt everywhere else; he almost welcomed the new distraction when he came face-to-face with Yugi. Apparently, he was the one who nearly broke his fingers, as he was no longer at the foot of Seto’s bed, but right beside him, one hand on his laptop and the other gripping the ridiculous railing trapping him inside.

“Did you hear a goddamn word I said?” Yugi’s voice was raised, and his eyebrows were furrowed the way _His_ were when _He_ was angry, but there was a shininess to his eyes that suggested tears were about to fall. Seto must have paused too long trying to figure out what Yugi was feeling, because he growled in frustration, and smacked his hand on the laptop again. “Well? Answer me!”

Seto said the first thing that came to mind: “I was using that.” When Yugi only seemed to get angrier, the voice in his head admonishing him was Gozaburo’s. _Another wrong answer, Seto._

“I know, that’s why I stopped you,” Yugi said, a paradoxical laugh escaping him. He shook his head, taking a step back from the bed. “I don’t know why I bothered. Of course, you care more about your fucking computer than you do about your brother’s suffering; if you cared, you wouldn’t have left in the first place.”

“Don’t try to tell me how I feel about Mokuba.” Seto’s own brow furrowed, and he sat up as far as he could without causing his IV to become further dislodged. “I care about Mokuba more than you’ve cared about anything in your entire life. _I_ got him out of that orphanage, _I_ made sure he lives in luxury! Everything I’ve done, _everything_ , was for him.”

By the time he was finished, his chest was heaving, and he could feel his pulse thudding in his throat, but he kept his face as impassive as he could. It seemed that Yugi wasn’t done, however, because he squeezed his eyes shut and grabbed at his hair, pulling it hard enough that Seto knew it must be causing him pain. After a few moments, he released his hair and rounded on Seto once more, tears falling down his cheeks.

“God, do you listen to yourself when you talk?” he shouted. “Was forcing Mokuba to run a corporation at fifteen years old all for him? Was it in his best interest to abandon him, just so you could play a game against a dead man? In what possible world were any of those things good for your brother?”

Seto opened his mouth, but all he could get out was, “But—” before he was cut off by Yugi.

“No, shut up and listen to me. Do you realize how much your stupid stunt cost him?” Seto clenched his fists, his mouth set in a stern line, but Yugi didn’t stop talking. “Mokuba is still a child; he should be going to school, making friends, getting invited to parties. But because you decided to disappear, Kaiba Corp is his responsibility. He’s had to grow up so fast, Kaiba, and he’s exhausted, all because you said he was ‘in charge.’ This is exactly what Gozaburo did to you, and you’re repeating it with Mokuba? What the _hell_ were you thinking?”

Somewhere in the midst of Yugi’s speech, tears had formed at the corners of Seto’s eyes, but he only let them fall at that last statement. “I wasn’t thinking!” he yelled, surprising himself his volume. Yugi ducked his head, but Seto didn’t move to maintain eye contact. He instead focused on where Yugi’s eyes had been, which made his gaze fall on the generic seascape painting on the wall across from his bed. “I wasn’t thinking, I didn’t plan anything,” he continued, almost unconscious of the way he was pounding his fist into his thigh in a regular rhythm as he spoke. “I just—I couldn’t take it anymore. I know I screwed up, I know what a wretched, selfish person I am, but—this was the only way.” _Feelings of self-hatred, backed up by evidence—higher than normal, likely triggered by failure to complete experiment._

He paused, finally ceasing the assault on his thigh, which ached in an all-too familiar way. “Kaiba,” Yugi said, sounding—sad? Pitying? Disgusted?—but Seto made a distressed noise that stopped Yugi from continuing.

The seascape he’d fixated on seemed to taunt him, and he imagined himself sinking into its waves, tossed about wherever the current took him. Once he felt sufficiently drowned, he opened his mouth again.

“Going to that place—defeating _Him_ —was the only way I could finally end all this. And I didn’t even beat him. And now, Mokuba—” He stopped speaking abruptly when he realized he was about to sob, squeezing his eyes shut tightly in an attempt to stop his body from betraying him. His voice was still thick with emotion when he forced himself to finish. “Mokuba deserves better than me. Maybe if I had—” Seto coughed twice, breathed in against his wishes, “—had stayed with _Him_ , none of this would have happened.”

Silence fell; all Seto could hear was his labored breathing and the beeping of the heart rate monitor he was attached to. If it had been monitoring anybody else during an outburst like that, it might have raised an alarm, but Seto’s heart rate had always been low. He didn’t dare open his eyes. Yugi was surely furious, or at the very least, disappointed, and he didn’t think he could face an expression like that right now. So, they remained shut, until he felt a hand on his shoulder, when they snapped open of their own accord. _Jumpiness; a pre-existing condition._ When he did, he found Yugi’s violet eyes staring into his own, tear tracks down his cheeks, and his mouth set in a grimly determined line.

“I think—” Yugi started, but stopped to clear his throat. “I think I should come stay with you and Mokuba for a while. Once you get out of here, I mean.”

Seto raised an eyebrow; why had Yugi changed the subject? “What, are you sick of living above your second-rate game shop? Why do you think I would be so charitable as to allow you to live in my home?” _Too rude, god damn it, why can’t you fucking speak right?_

“This isn’t about me!” Yugi’s voice was loud enough that it made Seto cringe, ducking his head even as he maintained eye contact. The hand left Seto’s shoulder, balling into a fist by Yugi’s side. “God, I don’t care about how big your house is, or your servants, or how much your wine cooler is worth. I’m asking to stay with you because I think you’re suicidal, and I want to be there to make sure you don’t kill yourself!”

Yugi was out of breath, glaring at Seto. He hated that it reminded him so much of _Him_ ; the way _His_ brow furrowed when he walked into _His_ throne room, the way _He_ had scolded him. It hurt more, somehow, hearing it from Yugi than it did from _Him_ ; though, most things involving _Him_ were different for Seto.

But, wait. “Kill myself?” Seto exhaled sharply from his nose. “Don’t make me laugh. I’m not going to throw myself out of the Kaiba Corp building the second something goes wrong. You of all people should know that I’m not my stepfather.”

Yugi closed his eyes, breaking the eye contact they’d maintained since Seto’s outburst, and squeezed his fists, but his voice was steady when he spoke. “No, I don’t think you would kill yourself deliberately. But, if you _had_ died in your dimension-crossing experiment, would you regret it? Were you scared of that happening?”

That thought had not occurred to Seto. As he thought it over, however, he came to a realization; no, he would not have minded if something had gone wrong. Even if he had gotten the calculations wrong, and the ship had exploded in midair…he would be reunited with _Him_ in whatever afterlife there was—assuming there _was_ an afterlife. And if there wasn’t? He would cease to exist: no more pain, no more regret, no more guilt.

Something in Seto’s expression must have changed, because Yugi nodded once, then looked him in the eyes once again, fierce despite the tears that continued to spill over his eyelids. “Right, that’s what I thought. Kaiba—” Yugi paused, swallowing audibly. “—Seto, you can be suicidal even without actively planning a suicide attempt. You know that, right?”

The use of his first name sent Seto reeling, but he didn’t want to back down yet. “So what? As long as I’m not going to actually do it, there’s no reason for you to invade my home.” He felt a bit like a cornered rattlesnake, striking without intent to really bite, in hopes that it would get Yugi to run away.

For his part, Yugi was standing his ground. Even though Seto knew he was glaring with as much force as he could muster, Yugi hadn’t looked away. For the first time, Seto realized just how tall he had gotten in the months since the incident with Diva; really, since Battle City. He was still decently short, but now he must be—what, five foot five? Five foot six?

“That’s not gonna cut it.” Oh, Yugi was talking, and he sounded angry. _Pay attention! Stop slipping up!_

“What, do I have to provide a bill of flawless mental health before you’ll let me live alone in my own home?”

Yugi’s mouth dropped open, and his eyes widened, in what was either fear or disbelief, Seto couldn’t tell. “In case you’ve forgotten, you _don’t_ live alone, Seto. This is as much for Mokuba’s sake as it is for yours.”

Seto cringed, screwing his eyes shut again. He could not argue with that. In fact, it occurred to him that for all the planning he had done to make this trip happen, he hadn’t thought about Mokuba’s wellbeing at all. He’d promised Mokuba that he would be his father now, and what had he done to show it? Abandoned him to run a business as a child.

When he didn’t respond, Yugi sighed. “Seto, I understand better than you think. When Atem left—” Seto cringed at the name— “I was despondent. I could barely get out of bed, let alone do anything else I was supposed to. I understand what it’s like to be lost in your grief. But there is a way out, I promise, and if I can help with that, I want to, more than anything.”

It took three attempts to force words from his too-thick throat: “You’re right.”

“Huh?” Yugi sounded genuinely startled, as though he wasn’t expecting Seto to speak.

 _More likely, he wasn’t expecting you to agree, since you’re nothing if not stubbornly wrong_ , said Gozaburo’s voice in his head. Seto shook his head, hoping to clear the voice from his mind, but only succeeded in exacerbating his headache.

“I said, you’re right. I clearly can’t care for Mokuba in this state. Speak with Isono as soon as you can, he’ll set up sleeping arrangements.”

“You’re just…agreeing, then.” Yugi’s voice was cautious, slow. Seto didn’t appreciate being spoken to like a wild dog, but he supposed it was appropriate.

“It’s what you wanted, right? Why are you being so hesitant?”

“I just—” Yugi cut himself off, eyes finally softening again. “Thank you, Seto.”

Suddenly, Seto’s hand was being taken in Yugi’s. Seto stiffened, reflexively, but Yugi didn’t pull away. His palm was warm; Seto’s hands were always cold, and they relished the heat they were able to steal.

How long Yugi stayed, holding his hand in silence, Seto couldn’t say. Hours, days, more probably minutes—he wasn’t keeping track. He was brought back to reality by Yugi’s hand squeezing gently, then letting go, forcing his hand to drop back onto the sheets. His gaze dropped to his abandoned extremity, noting how easily it blended in with the colorless fabric.

“I should let you rest,” Yugi was saying, face red. Was he hot? Embarrassed by having to hold Seto’s hand?

“I…suppose that’s for the best,” Seto found himself saying, even though he could _feel_ the pull of his body toward Yugi’s, looking for more of that heat. “You have Isono’s number, I assume?”

Yugi nodded once, then cleared his throat, causing Seto to look at him. And, oh, he was smiling, the soft smile Seto had only seen given to his friends, never his irascible rival. “I’m glad you’re alive, Seto,” he said, tenderly.

Seto couldn’t say anything: he just stared at Yugi, eyes following him as he collected his things and wrapped his scarf back around his neck. Before he left, he turned back, giving Seto a little wave and a smile. If Seto smiled back, he couldn’t tell— _facial paralysis? I wish._

Then, Yugi walked out the door. And Seto was left alone, once again. However, he felt lighter, somehow, even as he was face-to-face with his grief. Yugi had offered a hand, ready to pull him out of the turbulent sea. He just had to accept it.

He wished it wasn’t so hard.

**Author's Note:**

> Check me out at millenniumpuzzle on Tumblr for more shenanigans like this.


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